The broad objective of the proposed research is to determine the biological function of alpha-actinin in biological movement systems and how this function is related to the physiological roles of actin and actin-binding proteins such as tropomyosin, filamin, and actin-binding-protein in movement. Actin seems to have both cytoskeletal and cytocontractile functions in cells, and alpha-actinin has been proposed to bind actin filaments to plasma membranes in a variety of cells. These membrane-bound actin filaments disperse during cell division and cell transformation. Attempts will be made to determine whether any interaction, possibly mediated by alpha-actinin or an alpha-actinin-actin complex, exists among the three filament systems found in most animal cells: 1) the microfilament system; 2) 10-nm intermediate filaments; and 3) microtubules. The specific objectives of this research are: 1) to detect and locate alpha-actinin and other actin-binding proteins that may be related to alpha-actinin in different nonmuscle cells; these studies will use antibody localization techniques and biochemical assays of crude extracts of cells; 2) to study the alpha-actinin-actin and possible alpha-actinin-membrane interactions in the presence of actin and different actin-binding proteins; these effects will involve in vitro studies using purified proteins and specific proteolysis with a Ca2 ion-activaed protease; 3) to determine whether alpha-actinin binds to tubulin or desmin and could thereby link the three filament systems observed in cells; these studies will use in vitro mixtures of purified proteins followed by attempts to determine whether any binding can be detected; and 4) to ascertain the effects of microinjected alpha-actinin antibodies or alpha-actinin on microfilament organization in cultured cells; these efforts will involve observation of cells following microinjection to determine whether alpha-actinin antibodies or alpha-actinin will alter microfilament structure in cells.